United States
                           Environmental Protection
                          Municipal Environmental Research
                          Cincinnati OH 45268
                           Research and Development
                          EPA-600/D-83-117  Oct. 1983
                          Chemical  Reactions of Aquatic Humic
                             Materials with Selected Oxidants
                     R. F. Christman1, J. D. Johnson, D. S. Millington, and A. A. Stevens2
A study was conducted to identify the specific organic
reaction products of natural aquatic humic materials with
selected oxidants (KMnO*, HOCI, CI02, O3, and mono-
chloramine). Fulvic and humic acid fractions were isolated
from two southeastern  U.S. surface waters using a
combination of XAD-8 adsorption, acid precipitation, salt
removal, and freeze drying. One or both fractions were
exposed to each  oxidant  under controlled  laboratory
conditions at various oxidant/carbon molar ratios (KMnO4,
0.75 to 2.2; HOCI, 4; CI02, 1.0;  03,  4.8 to 7.3; mono-
chloramine, 2.0 and  10.0). The  principle objective was
qualitative identification of reaction products; therefore
strict efforts were not made to use reactant concentrations
at water treatment plant levels or to keep oxidant/carbon
ratios at identical levels for the different oxidants studied.
Reaction products were identified by gas chromatography/
mass spectrometry (GC/MS) after solvent extraction and
derivatization. The two most reactive oxidants in terms of
the number of identified products and overall yields were
KMnO* and HOCI, though products were identified after
exposure to CI02 and O3. Certain similarities exist among
the oxidation products identified from all oxidants, though
the presence of chorine in reaction products depends on its
presence in the oxidant.

The macromolecular structure of aquatic humic and fulvic
acids (inferred  from the  nature of NaOH and KMnO4
degradation products) may consist of (a) single-ring aro-
matics with mainly three to six alkyl substituents, carboxylic
acid, ketone, or  hydroxyl groups, (b) short aliphatic carbon
'University of North Carolina at Chapel Hill, NC 27514
2Municipal Environmental Research Laboratory, USEPA, Cincinnati OH
                     chains, and (c) polycyclic ring structures, including poly-
                     nuclear aromatics, polycyclic aromatic-aliphatics, and fused
                     rings involving furan and possibly pyridine. Though the
                     structural relationships between these fragments could not
                     be established, these fragments are believed to be associ-
                     ated with humic macromolecules through carbon-carbon

                     The degradation products of fulvic and humic fractions from
                     two water sources were qualitatively similar to each other,
                     but some quantitative differences  were found. The  dif-
                     ferences found between fulvic and humic fractions isolated
                     from each  source were  smaller than the  differences
                     between the fractions isolated from the different sources.

                     The principal identified chlorination products of the fulvic
                     and humic acid samples studied were, in order of decreasing
                     abundance, trichloroacetic acid, chloroform, and dichloro-
                     acetic and dichlorosuccinic acids. For fulvic acid, the total
                     yield of identifiable products was approximately 14 wt% of
                     organic reactant (compared with 25 wt% for KMnO<). The
                     principal products accounted for  approximately 4 wt% of
                     original total organic carbon (TOC).  Of these, product
                     composition was approximately 69% trichloroacetic acid,
                     19% chloroform,  9.5% dichloroacetic acid, and 4.5%
                     dichlorosuccinic acid, based on product carbon per gram of
                     starting fulvic acid. Thus trichloroacetic acid (not chloro-
                     form) was shown to be the dominant chlorination product.
                     Collectively, these four products accounted for 53% of the
                     system total organic halogen (TOX).

                     Chlorine dioxide  produced fewer  identifiable  reaction
                     products than chlorine, with product composition  domi-
                     nated by C-i-Ciodibasic aliphatic acids. Chlorinated products
                     of CI02 included trace  amounts of dichloroacetic acid.

monochloromalonic acid, and monochlorosuccinic acid. No
products of the reaction of monochloramine with f ulvic acid
were identified by GC/MS.

This Research Brief was  developed  by  the principal
investigators and EPA's Municipal Environmental Research
Laboratory, Cincinnati, OH, to announce key findings of the
research project that is fully documented in the reports and
publications listed at the end.


Humic substances account  for significant  but variable
proportions of the organic matter in soils and sediments
and of the soluble organic matter in fresh and sea waters.
Despite extensive research concerning the formation and
environmental impact of waterborne organics, the chemical
structures of aquatic humic substances are still not known
to the desired level of certainty.

These natural products are apparently acidic, hydrophilic,
complex materials that range in molecular weight from a
few hundred to many thousands. Humic materials isolated
from soils have been  extensively studied, but it cannot be
presumed that aquatic humic materials are similar except
for chemical complexity. Degradation studies of soil humic
acid have produced evidence of both aromatic and aliphatic
constituents,  but few degradation studies have  been
conducted on aquatic humics. Furthermore, it is not known
whether aquatic humic and fulvic materials isolated from
different sources exhibit chemical similarities.

Our experimental approach was therefore to expose natural
humic and fulvic acid preparations to a nonhalogenated
oxidant (alkaline  KMn04) under  controlled  conditions.
Knowledge of the yield and reaction product distribution
should be useful for (a) increasing our understanding of the
macromolecular structures of  undergraded humic and
fulvic materials, (b) determining the differences that may
exist between humic substances from waters  of different
geographical locations, and (c) establishing a  baseline of
oxidation products with which chlorination products can be

Certain experimental procedures are common to all aspects
of this research. The XAD-8 isolation/purification process
and the GC/MS systems employed are fully described in
project  publications  (6,8,11). Except where  specifically
stated in these publications,  GC/MS  identifications were
based on a set of criteria that includes the following for each
compound: (a) electron impact (El) mass spectrum, (b)
chemical ionization (Cl) mass spectrum for molecular ion
confirmation, (c) elemental composition of major ions in the
El spectrum by means of low resolution, accurate mass
measurement, (d)comparison of mass spectra with authen-
tic speciments when available, and (e) comparison of GC
retention  time with that of an authentic specimen when
available. Several factors in the analytical protocol of this
research were important because many of the compounds
identified are not available in mass spectral libraries. These
factors are the use of capillary GC columns, rapid MS scan
rates (generally 1 to 2 sec, compatible with the capillary GC
profiles), use of double-focusing mass spectrometer, and
the  acquisition of accurate mass data without serious
compromise to sensitivity or scan speed by using low

KMnO4 Oxidation and Base Hydrolysis

The structures and yields of more than 70 compounds were
determined in the product mixtures of fulvic and humic acid
fractions exposed to  NaOH  hydrolysis  and/or  KMnO*
oxidation (1,8). These products were classified, according to
structural similarity, into the six groups shown in Table 1.
The product distributions and overall yields for fulvic and
humic acid samples from the two different sources were
remarkably similar. The maximum yield of GC/MS detec-
table degradation products was approximately 25 wt% of
starting material. Loss of volatiles (presumably COz) during
oxidation was estimated at 20% to 25% of the original TOC,
so that overall accountability of degradation products can
be estimated as 35% of original TOC if it is assumed that
identified products average 50% carbon. Thus only about
one-third of starting material is represented by the identi-
fied compounds, though  most of the  chromatographable
material was identified (see Table 1).

Except for Black Lake fulvic  acid, aliphatic  dibasic acids
were the major base hydrolysis products for all the humic
acid and fulvic acid samples. All of the base hydrolysis
products identified were also present in permanganate
oxidation products, but carboxyphenylglyoxylic acids were
not found in the base hydrolyzed samples.

Permanganate oxidation  of both fulvic and humic acids
produced benzenecarboxylic acids as the dominant identi-
fied product category with the tri-, tetra-, and pentacarboxy
acids presenting the principal substitution  patterns. Fulvic
and humic acids also gave high relative yields of oxalic,
malonic, and succinic acids.

A significant difference was found among the aliphatic acid
products. Most of the monobasic acids and the long-chain
dibasic  acids that were  identified among the  humic acid
oxidation products were  not detected in those of fulvic acid
samples. This difference may indicate that the long-chain
acids were associated with the less soluble hydrophobia
humic  acid macromolecules  and were  released  as the
humic acid macromolecules were degraded.

Under the conditions of experiments conducted  in this
study, the permanganate oxidation is believed to oxidize the
alkyl side chains of arenes (aliphatic-aromatic compounds)
and result in the formation of aromatic acids and saturated
aliphatic acids, the permanganate oxidation data indicate
that the principal number of alkyl constituents  on the
aromatic rings in the humic macromolecule is in the range
of three to six to account for the predominance of the
benzenepolycarboxylic acid derivatives. Two facts support
the hypothesis that the length of these interaromatic alkyl
chains  may be relatively short. First, the Cz-C* aliphatic
dibasic acids dominate the dibasic  acid structures found.
Second, the increase of benzenecarboxylic acid yield for
KMnO4 (compared with NaOH hydrolysis) is significantly
greater than the increase in aliphatic dibasic acid yield. This
result could occur if some of the alkyl bridges were short
enough to yield only aromatic acids and CO2 after oxidation.
The survival of some long-chain dibasic acids after KMnO4

Table 1.     Summary of Results of KMnO4 Oxidation and NaOH Hydrolysis of Aquatic Humic Acidsand Fulvic Acids from Black Lake
          and Lake Drummond*
                                                    Black Lake
                                                                                      Lake Drummond
     Compound Class
KMnO,    Oxidation    NaOH   Hydrolysis   KMnOt   Oxidation    NaOH   Hydrolysis
 H/lf       FA       HA        FA       HA        FA       HA        FA
Benzenecarboxylic acid methyl
  esters (29 compounds)

Furancarboxylic acid methyl
  esters (5 compounds)

Carboxyphenylglyoxylic acid methyl
  esters (8 compounds)

Aliphatic monobasic acid methyl
  esters (14 compounds)

Aliphatic dibasic acid methyl
  esters (14 compounds)

Aliphatic tribasic acid methyl
  esters (5 compounds)


Identified Percentage of
  Total GC Peak Area
142.71     127.77     5.36

 13.61      9.98     0 14
           4.70     0.00
           0.82     0.72
           56.48     10.62
 5.56     110.71    104.14      2.96

 0.16      21.10     26.64      0.36

 0.00       5.77      5.61      0.00
                                                 6.14      0.54
                                       98.06     98.07    11.30




  0.62       1.47     0.29

21307     201.22     17.13
 0.39       4.94      4.52      0.45       0.51

13.17     255.42    245.12     15.61      12,57
 "Yields (mg) resulted from 1.0 g of starting humic samples.
 \FA, fulvic acid: HA. humic acid.

is established by the complete data, but it is not possible to
evaluate the possibility that successive terminal oxidation
of longer alkyl substituents could produce the same result.

An attractive assumption is that most of the carboxyl groups
observed among these products constitute sites of carbon-
to-carbon linkages in the undegraded macromolecule. This
assumption is supported by the data in Table 1, which show
that the total yield of acids produced by base hydrolysis is
much  lower. Some of the acid  groups must  be bound
originally in ester linkages, probably with other aromatic
moieties (to account for base hydrolysis yields). But most of
the alkyl constituents of aromatic rings must  be carbon
chains,  which  resist sodium hydroxide  hydrolysis.  In
addition, some of the carboxylic acids must be present as
free groups in the undegraded macromolecule to account
for the acidity of aquatic humics.

In general, the  predominant products found in Black Lake
samples are  also the  predominant  products'  in Lake
Drummond samples.  Based on the results  of this study,
aquatic humic materials from the two sources are believed
to be qualitatively similar, but quantitative variations were
observed in the composition of humic degradation mixtures
from the different sources. Whether these variations are
related to seasonal changes, various stages of  the humi-
fication process, or vegetative conditions indigenous to the
source is not known.

Reaction  with Chlorine

More than  100 reaction products were identified from
exposure of humic acid to chlorine at a pH of 12 and from
exposure of fulvic acid to chlorine at neutral pH (4,7,10,13).
Principal aliphatic products (only the C4 chain length and
less) are  shown in Table  2. Concentrated ether extracts of
the fulvic acid  reaction products were light green, had a
sweet/acid odor  reminiscent of chloroform  or  some
                   chlorinated acid, and reacted vigorously with diazomethane.
                   Blank extracts were colorless, had no such odor, and had
                   little visible reaction with diazomethane. In these respects,
                   the concentrated fulvic acid samples and blanks resembled
                   their counterparts from the high-pH humic acid work.

                   The initial HOCI/C molar ratio for the neutral pH fulvic acid
                   reaction was 4, like that of pH 12 humic acid work. This pH 7
                   reaction with chlorine was apparently more rapid than the
                   pH 7 humic acid high-pH reaction, judging from the rates of
                   color bleaching. The pH  7 fulvic acid chlorine exposures
                   were therefore  held  24  hr, while humic  acid high-pH
                   exposures were allowed to reach 48 hr.

                   The  majority of the pH 7 fulvic  acid  chlorine reaction
                   products contained chlorine, whereas most of the pH  12
                   humic acid chlorine reaction products did not. In addition,
                   many of the non-chlorine-containing fulvic acid products
                   were present in the system control or sample blank. An
                   adequate system control for the humic acid experiments
                   was  impossible  to  obtain, but the reaction  products
                   contained relatively large amounts  of tatty acids (C16
                   dominant) that were not observed in the fulvic acid system

                   Nearly all of the products identified in the humic acid
                   experiment were methyl esters, presumably derived from
                   the methylation  of  mono-  and  polybasic  acids.  These
                   included mono-  and dibasic, saturated  and unsaturated,
                   chlorine-substituted and unsubstituted acids. Most of the
                   more than 100 compounds identified were not chlorinated;
                   however, di- and trichloroacetic acid, dichlorosuccinic acid,
                   and dichloromaleic and dichlorofumaric acid were formed
                   in  especially  high yield. A large number of  mono- and
                   dibasic unchlorinated aliphatic acids from acetic and oxalic
                   acid up to the C2? monobasic fatty acid were identified. The
                   dibasic unchlorinated aliphatic acids were generally of low
                   molecular weight (C2-Cio). These aliphatic acids may  be

ring-cleavage products and were present in relatively low
yield. Benzenecarboxylic acids (including mono- to hexa-
carboxy acids in all isomers as well as small quantities of
methyl-substituted  aromatic acids  and  isomers  of
carboxyphenyl-glyoxylic acid) were also detected.  Notice-
ably missing from the  aromatic series were chlorine-
substituted aromatic acids and aromatic acids with aliphatic
side chains other than methyl. This pattern is similar to that
found  with  permanganate  oxidation,  suggesting  that
chlorine  in alkaline solution  is capable of oxidizing  side
chains down to terminal carboxyl groups on the aromatic

Several general features of the fulvic  acid chlorination
product distribution can be stated. First, except for chloro-
form and chloral,  all components were methyl esters. A
reasonable assumption is that they were free acids in the
original  aqueous  sample, which serves  to  explain the
diazomethane reaction. Second, unlike the pH 12 humic
acid chlorination products, most of the pH  7 fulvic  acid
degradation  products contained chlorine. They  include
chloroform; chloral; methyl mono-, di-, and trichloroacetate;
dimethyl  dichloromalonate;  dimethyl  dichlorosuccinate;
dimethyl dichloromaleate;  methyl 2,2-dichloropropionate;
dimethyl  chlorosuccinate; dimethyl  chloromaleate;  and
various  other  less abundant  compounds.  Even some
bromodichloromethane was  formed,  which  must result
from bromide ion impurity activated by HOCI. No chlorinated
aromatic products were found.

Finally,  most  of  the compounds from the  fulvic  acid
reactions not  containing  chlorine were  aromatic.  They
included various isomers  of  dimethylphthalate; benzene
tricarboxylic acid trimethyl ester; benzene tetracarboxylic
acid tetramethylester; and other aromatic methyl esters.
These compounds did not clearly result from the chlorina-
tion reaction,  since the sample blank or system control
revealed their presence in similar quantities. Derivatives of
phenylglyoxylic acid were found in the chlorinated reaction
mixture  (not in system  control), an  interesting group of
structures.  Confirmation could not be achieved in these
samples, since no standards were available. They were
found in the humic acid chlorination product extract as well
as in potassium permanganate degradation product mix-
tures from aquatic humic  and fulvic  acids (10).,Liao et al.
proposed that such compounds can result from the oxida-
tion of fused ring systems present in the humic (or fulvic)
 macromolecule (8).

 A direct comparison of the yields of various compounds
 from the fulvic and humic acid chlorinations is unrealistic,
 since different reaction times were used. But both reactions
 clearfy produce extremely similar products that contain a
 predominance of small chlorinated acids. TOX analyses on
 the concentrated ether extracts revealed that the fulvic
 sample  contained 60% more organically bound  chlorine
 than the humic sample, even though the reaction time of
 the latter was twice as long. This observation agrees with
 the expected  greater electrophilic  substitution  of  HOCM
 present at the more acidic pH values compared to the OCI"
 present at pH  12.

 The yields of  the four principal chlorination products of
 fulvic acid  were estimated initially by adding known
                                                          Table 2.
          Short-Chain Chlorination Products of Aquatic
          Humic and Fulvic Acids


















ch/oroethanoic acid
(chloroacetic acid)

dichloroethanoic acid
fdich/oroacetic acid)

trichloroethano/c acid
(trichloroacetic acid)

2,2-dichloropropanoic acid

3,3-d/ch/oropropenoic acid

trichloropropenoic acid

dichloropropanedioic acid
(dichloromalonic acid)

butanedioic acid
(succmic acid)

chlorobutanedioic acid
fchlorosuccintc acid)

2,2-dichlorobutanedioic acid
(2,2-dichlorosuccinic acid)

c\s-chlorobutenedioic acid
(ch/oroma/eic acid)

cis-dichlorobutenedioic acid
(dichloromaleic acid)

trans-dichlorobutenedioic acid
Idichlorofumanc acid)
*a. Confirmed El spectrum and GC retention time comparison with
   authentic specimen.
 b. Confirmed, El spectrum comparison with authentic specimen.
 c Confident, El spectrum, Cl spectrum, no authentic specimen aval/able.
 d Tentative, data relatively incomplete in some respect
t Observed only in fulvic acid samples

quantities  of an internal standard (methyl-p-chlorobenzo-
ate) to ether extracts and  measuring  GC/MS peak-area
ratios derived from selected  ion current  chromatograms
(e.g., 117/139 for trichloroacetic acid). Actual weights of
compounds of interest were then calculated from standard
curves,  and  accurate concentrations in the  aqueous
reaction mixture of the two principal products (trichloro-
acetic  acid  and chloroform) were then  determined  by
validated methods. An isotope dilution method developed in
our laboratory (13) was used for trichloroacetic acid, and
the standard EPA purge and trap method was employed for
chloroform.* Yield values are summarized in Table 3. The
values for the two minor products in Table 3 are  probably
underestimated  since they were determined only in the
ether extract.

The  data  establish  that  trichloroacetic acid  (and  not
chloroform) is the dominant reaction product, and that the
 •Method 501 1, USEPA, Cincinnati, Ohio 45268

 Table 3.    Yields of Fulvic Acid Chlorination Products
   mg        mg      Percent  Percent
Product;'g   Product C/g  Original   Final
Fulvic Acid  Fulvic Acid C   TOC    TOX
Trichloroacetic acid
Dichloroacetic acid
Dichlorosuccmic acid
32 1
 *Sum of dichloroacetic and dichlorosuccmic acids.

four chlorinated products shown in Table 3  collectively
account for 53% of the observed TOX (13).

Reaction with Other Oxidants

None of the other oxidants investigated in  this  study
produced appreciable amounts of degradation  products
with aquatic fulvic acid compared with the permanganate
and chlorine product data. Small amounts of products were
identified with chlorine dioxide and ozone.

Reactions between CIO2 and fulvic acid at pH  values of 3
and 7.8 were  found to be  rapid but  limited.  Neither
increased oxidant concentrations nor reaction  times of up
to 24  hr seemed to influence  the  extent of  reaction.
Recovery of TOC after reaction termination average 70%
under both  pH conditions; thus, an average of 30% of the
original fulvic carbon was apparently converted to COa or
other extremely volatile compounds. The amount of ether-
extractable carbon was on the order of 10% to 14%; ethyl
acetate extracted an additional 3% to 4% of the original
carbon. The portion of this extractable carbon that was also
chromatographable was not determined, but it was evident
that identifiable products represented  a small fraction of
the initial fulvic material. The bulk of the organic substrate
remained in aqueous solution, implying  that  it was not
sufficiently degraded to be analyzable by these techniques,
providing additional evidence  that little overall reaction
occurred between CI02 and fulvic acid.

Four major  classes of compounds were represented in the
degradation mixtures of both pH 3 and 7.8 reactions with
CIO2: benzenepolycarboxylic acid methyl esters, aliphatic
dibasic acid dimethyl esters, carboxyphenylglyoxylic acid
methyl  esters,  and  aliphatic  acid monomethyl esters.
Benzene di-  and tricarboxylic  acid  methyl  esters and
palmitic acid methyl ester, plus three  of its branched
isomers, were dominant  components  of  the sample ex-
tracts. But these aromatic compounds were also detected in
abundance  in the undegraded control and therefore cannot
be regarded as unique products of the  CI02  fulvic acid
reaction. Individual products or product  abundances not
observed in system  control samples  included  carboxy-
phenylglyoxylic acids, methylfurancarboxylic acid, dibasic
aliphatic acids (C4-Cio), and small quantities of dichloro-
acetic acid,  monochloromalonic acid, and monochlorosuc-
cinic acid.  The  dibasic  aliphatic acids  were  the  one
structural category found  in greater abundance with CI02,
than with permanganate and chlorine (2,9). The results
obtained with ozone were similar to those with CI02, except
that chlorinated derivatives were absent in product mixtures
(11). The cumulative ozone demand of fulvic acid varied
between 1 and 2 moles Oaper mole carbon. For experiments
in which a ratio of 5 moles Oaper mole carbon existed, 20%
of the original TOC was converted to C02 or other volatile

Of the fulvic acid degradation agents tested, monochlor-
amine is apparently the least effective, since no reaction
products were identifiable  in  ether extracts of reaction
mixtures (12) (though fulvic acid solutions exerted a demand
of 0.13 mole of monochloramine per mole of fulvic carbon
after 24 hr at pH 9). Colclough et al. (2,9) observed by way of
comparison that fulvic acid consumed 0.3 mole CI02 per
mole of carbon at pH 7.8.


The following publications collectively contain the complete
findings of this research project. The Ph.D. thesis (#1, Liao)
is available from University Microfilms, P.O. Box 1346, Ann
Arbor, Ml  48106.  Completed  master's  thesis  (#2,3,
Colclough and Norwood) are available from R. F. Christman,
Department of Environmental Sciences and Engineering,
University of North Carolina, Chapel Hill, NC 27514. These
and articles that are in preparation (#11,12,13) are  also
available from R.  F. Christman.

  1.  Liao, Wenta, "Characterizaton of Aquatic Humic Sub-
     stances," Ph.D. Dissertation, Department of Environ-
     mental Sciencesand Engineering, University of North
     Carolina at  Chapel Hill, August 1981.

 2.  Colclough,  Carol,  "Organic Reaction  Products of
     Chlorine Dioxide and Natural Aquatic Fulvic Acids,"
     M.S.P.H. Thesis, Department of Environmental  Sci-
     ences and Engineering, University of North Carolina
     at Chapel Hill, December 1981.

 3.  Norwood, D. L,  "A Comparison  of  GC/MS  and
     MS/MS for Complex  Mixture Analysis," M.S.P.H.
     Thesis,  Department of Environmental Sciences and
     Engineering, University of North Carolina at Chapel
     Hill, December 1981.

 4.  Christman,  R.  F., Johnson, J. D., Pfaender, F. K.,
     Norwood, D. L.,  Webb,  M. R.,  Hass, J.  R.,  and
     Bobenrieth, M. J., "Chemical Identification of Aquatic
     Humic Chlorination Products," In:  Water Chlorina-
     tion: Environmental Impact and Health Effects, Vol. 3,
     Robert L. Jolley  et al. (eds.),  Ann Arbor  Science
     Publishers,  Ann Arbor, Michigan,  1980.

 5.  Norwood, D. L., Johnson, J. D., Christman, R. F., Hass,
     J. R., and Bobenrieth, M. J., "Reactions of Chlorine
     with  Selected  Aromatic Models  of Aquatic Humic
     Material,"Environ. Sci. and Techno/. 14, 187, 1980.

 6.  Christman,  R.  F., Liao, W., Millington, D. S.,  and
     Johnson, J. D., "Oxidative  Degradation of Aquatic
     Humic Material," In: Advances in the Identification
     and Analysis of Organic Pollutants in Water, Vol. 2,
     Lawrence H. Keith (ed.), Ann Arbor  Science Pub-
     lishers, Inc., Ann Arbor, Michigan, 1981.

 7.   Johnson, J. D., Christman, R. F., Norwood, D. L, and
     Millington,  D.  S., "Reaction  Products  of  Aquatic
     Humic Substances with Chlorine," Environ. Health
     Perspectives. 46, 63-71, 1982.

 8.   Liao, Wenta, Christman,  R.  F.,  Johnson, J.  D.,
     Millington, D. S., and Mass, J. R., "Structural Char-
     acterization of Aquatic Humic Material,"Environ. Sci.
     and Techno/., 16, 402-410, 1982.

 9.   Colclough, C. A., Johnson, J. D., Millington, D. S., and
     Christman,  R.  F., "Organic Reaction  Products  of
     Chlorine Dioxide and Natural Aquatic Fulvic Acid," In:
     Water Chlorination: Environmental Impact and Health
     Effects, Vol. 4, Robert L. Jolley et al. (eds.), Ann Arbor
     Science Publishers, Ann Arbor, Michigan, 1983.

10.   Norwood, D. L, Johnson, J. D., and Christman, R. F.,
     "Chlorinated Products from Aquatic Humic Material
     at Neutral pH," In: Water Chlorination: Environmental
     Impact and Health Effects. Vol. 4, Robert L. Jolley et
     al. (eds.), Ann Arbor, Michigan, 1983.

11.   Anderson, Linda, "Analysis of the Organic Reaction
     Products of Aquatic Fulvic Acid Ozonation," M.S.P.H.
     Thesis, Department of Environmental Sciences and
     Engineering, University of North Carolina at Chapel
     Hill, in preparation, 1983.

12.   Jensen, James, "Identification of  the Organic Pro-
     ducts of the Reaction of Aquatic  Fulvic Acid with
     Monochloramine," M.S.P.H. Thesis, Department of
     Environmental Sciences and Engineering, University
     of North Carolina at Chapel Hill, in preparation, 1983.

13.   Christman,  R. F., Norwood, D. L,  Millington, D. S.,
     Johnson, D. J., and  Stevens, A. A., "Identity and
     Yields of Major  Halogenated Products of  Aquatic
     Fulvic Acid Cnorination," submitted to Environ. Sci.
     and Techno/., January 1983.